Materials Science and Engineering Laboratory FY 2004 ... - NIST

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Materials for Electronics Characterization of Porous Low-k Dielectric Constant Thin Films NIST provides the semiconductor industry with unique on-wafer measurements of the physical and structural properties of nanoporous thin films. Several complementary experimental techniques are used to measure the pore and matrix morphology of candidate materials. The data are used by industry to select candidate low-k materials. Measurement methods that may be transferred to industrial laboratories, such as x-ray porosimetry, are developed. New methods are being developed to measure patterned low-k samples and to assess the extent of porous structure modification caused by plasma etch. Eric K. Lin and Wen-li Wu The future generation of integrated circuits requires porous low-k interlayer dielectric materials to address issues with power consumption, signal propagation delays, and crosstalk that decrease device performance. The introduction of nanometer scale pores into a solid film lowers its effective dielectric constant. However, increasing porosity adversely affects other important quantities such as physical strength and barrier properties. These effects pose severe challenges to the integration of porous dielectrics into the device structure. There is a need for nondestructive, on-wafer characterization of nanoporous thin films. Parameters such as the pore size distribution, wall density, porosity, film uniformity, elemental composition, coefficient of thermal expansion, and film density are needed to evaluate candidate low-k materials. NIST continues to develop low-k characterization methods using a combination of complementary measurement methods including small angle neutron and x-ray scattering (SANS, SAXS), high resolution x-ray reflectivity (HRXR), x-ray porosimetry (XRP), SANS porosimetry, and ion scattering. To facilitate the transfer of measurement expertise, a recommended practice guide for XRP was completed and will be available for industrial customers. In collaboration with industrial and university partners, we have applied existing methods to new low-k materials and developed new methods to address upcoming integration challenges. A materials database developed in collaboration with International SEMATECH is used extensively by SEMATECH and its member companies to help select candidate materials and to optimize integration processing conditions. This year, we also addressed the effects of the ashing/plasma etch process on the low-k material during pattern transfer. Often, surfaces exposed to ashing/plasma densify and lose terminal groups (hydrogen or organic moiety) resulting in increased 34 moisture adsorption and, thus, increased dielectric constant. HRXR measurements enable quantification of the surface densification or pore collapse in ashing-treated and/or plasma-treated blanket films. Figure 1: SAXS data of a test line grating created in a porous low-k film. Experimental data — solid symbol; model fit — red line. The top data was fit with a uniform cross-section whereas the bottom data was fit with a dense skin layer. Regions outlined by blue circle highlight the difference between these two models. A new method using SAXS was also developed to investigate the effect of plasma etch on patterned low-k films. Any densification of the sidewall may be observable by x-ray scattering from the cross-section of a patterned nanostructure. Preliminary SAXS work was carried out at Argonne National Laboratory using line gratings of low-k material. The feasibility of this approach is shown in Figure 1 where a surface layer densification is needed to fit the SAXS data. Contributors and Collaborators H. Lee, C. Soles, R. Hedden, M. Silverstein, T. Hu, R. Jones, D. Liu, B. Vogt, B. Bauer (Polymers Division, NIST); C. Glinka (NIST Center for Neutron Research); Y. Liu (International SEMATECH); Q. Lin, A. Grill, H. Kim (IBM); M. Ko (LG Chem.); H. Fu (Novellus); J. Quintana, D. Casa (Argonne National Laboratory); K. Char, D. Yoon (Seoul National University); J. Watkins (University of Massachusetts — Amherst)
Materials for Electronics Polymer Photoresists for Next-Generation Nanolithography Photolithography, the process used to fabricate integrated circuits, is the key enabler and driver for the microelectronics industry. As lithographic feature sizes decrease to the sub-100 nm length scale, significant challenges arise because both the image resolution and the thickness of the imaging layer approach the macromolecular dimensions characteristic of the polymers used in the photoresist film. Unique high-spatial resolution measurements are developed to reveal limits on materials and processes that challenge the development of photoresists for next-generation sub-100 nm lithography. Vivek M. Prabhu Photolithography is the driving technology used by the microelectronics industry to fabricate integrated circuits with ever decreasing sizes. In addition, this fabrication technology is rapidly being adopted in emerging areas such as optoelectronics and biotechnology requiring the rapid creation of nanoscale structures. In this process, a designed pattern is transferred to the silicon substrate by altering the solubility of areas of a polymer-based photoresist thin film through an acid catalyzed deprotection reaction after exposure to radiation through a mask. To fabricate smaller features, next generation photolithography will be processed with shorter wavelengths of light requiring photoresist films less than 100 nm thick and dimensional control to within 2 nm. To advance this key fabrication technology, we work closely with industrial collaborators to develop and apply high-spatial resolution and chemically specific measurements to understand changes in material properties, interfacial behavior, and process kinetics at nanometer scales that can significantly affect the patterning process. This year, we have continued to apply and advance unique measurement methods to provide structural measurement of fabricated nanoscale structures and new insight and detail into the complex physico–chemical processes used in advanced chemically amplified photoresists. These methods include x-ray and neutron reflectivity (XR, NR), small angle x-ray and neutron scattering (SAXS, SANS), near-edge x-ray absorption fine structure spectroscopy (NEXAFS), combinatorial methods, solid state nuclear magnetic resonance (NMR), quartz crystal microbalance (QCM), fluorescence correlation spectroscopy (FCS), and atomic force microscopy (AFM). Figure 1: NEXAFS instrument and spectra illustrating a homopolymer enrichment at the film surface for a model 157 nm photoresist blend. The mismatch in surface versus bulk composition illustrate interfacial limitations for sub 100 nm structures. Accomplishments for this past year include: advancement of photoresist–liquid interfaces for immersion lithography and developer distribution in ultrathin films (see highlight); photoresist component segregation (see Figure 1); quantification of the post-exposure bake time on the reaction–diffusion of photoacid 3D deprotection volume; first measurement of immersion and exposure dependence of the surface composition of base additives in 193 nm resist films; identification of key anti-reflective coating (ARC) components responsible for profile control problems and residual layer formation at the ARC-resist interface; quantification of environmental sensitivity by in-situ processing using NEXAFS; and quantification of the effects of developer and additives on the final resolution of lithographic features using a model reaction–front bilayer geometry. International SEMATECH has selected NIST in an effort to apply these fundamental measurements to identify materials sources of the fabrication limits of advanced photoresists. Contributors and Collaborators B. Vogt, E. Jablonski, C. Soles, W. Wu, C. Wang, R. Jones, T. Hu, M. Wang, D. VanderHart, C. Chiang, E. Lin (Polymers Division, NIST); D. Fischer, S. Sambasivan (Ceramics Division, NIST); S. Satija (NCNR, NIST); D. Goldfarb, A. Mahorowala, M. Angelopoulos (IBM T.J. Watson Research Center); H. Ito (IBM Almaden Research Center); C. Willson (University of Texas at Austin); R. Puligadda, C. Devadoss (Brewer Science); R. Dammel, F. Houlihan (Clariant Corporation) 35
Page 2 and 3: On the Cover: From the front cover
Page 4 and 5: ii Certain commercial entities, equ
Page 6 and 7: Table of Contents iv Materials for
Page 8 and 9: Technical Highlights Coherent Anti-
Page 10 and 11: Technical Highlights Use of Reverse
Page 12 and 13: Technical Highlights Profiling the
Page 14 and 15: Technical Highlights Dielectric Met
Page 16 and 17: Technical Highlights High-Throughpu
Page 18 and 19: Technical Highlights Polymer Librar
Page 20 and 21: Technical Highlights MALDI-MS Inter
Page 22 and 23: Technical Highlights Extraordinary
Page 25 and 26: Advanced Manufacturing Processes Th
Page 27 and 28: Advanced Manufacturing Processes Po
Page 29 and 30: Processing Flows and Instabilities
Page 31: Polymer Standards Producers, proces
Page 34 and 35: Biomaterials Structure-Property Rel
Page 36 and 37: Biomaterials Tissue Engineering Sca
Page 39: Materials for Electronics The U.S.
Page 43: Nanoimprint Lithography Nanoimprint
Page 46 and 47: Nanometrology Combinatorial Adhesio
Page 48 and 49: Nanometrology Gradient Reference Sp
Page 50 and 51: Nanometrology Characterization of C
Page 52 and 53: Safety and Reliability Ballistic Re
Page 54 and 55: Polymers Division FY04 Annual Repor
Page 65 and 66: Polymers Division Chief Eric J. Ami
Page 67 and 68: Carey, Clifton M.* clifton.carey@ni
Page 69 and 70: Hu, Tengjiao + tengjiao.hu@nist.gov
Page 71 and 72: Prabhu, Vivek M. vmprabhu@nist.gov
Page 73: Weir, Michael michael.weir@nist.gov
Page 76: Organizational Charts 70 Polymers D

Materials Science and Engineering Laboratory FY 2004 ... - NIST

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